BD9285F Datasheet, PDF (18/39 Pages) Rohm – Boost 1channel white LED driver For large LCDs

BD9285F
Datasheet
●3.4.4. how to set DCDC oscillation frequency
RRT which connects to RT pin set the oscillation frequency of DCDC.
○ the relationship between OSC and RRT (ideal)
R _RT
=
15000
f _SW [kHz ]
[kΩ]　
where fsw is the oscillation frequency of DCDC [kHz]
Ideal
Frequency (fsw)
RT
R
RT
GATE
CS
Rcs
GND
Figure 25. RT pin setting example
This equation is an ideal equation in which correction factors are not applied.
The adequate verification with an actual set needs to be performed to set frequency precisely.
[setting example]
If DCDC oscillation frequency is 200kHz, we can calculate the RRT as below.
R_RT
=
15000 ₌ 15000 _{= 75}
f _sw[kHz] 200[kHz]
[kΩ]　　
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TSZ22111・15・001
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TSZ02201-0F1F0C100030-1-2
11.Jul.2012 Rev.001